The ambient temperature in an operating room is low for a variety of reasons. A surgeon typically has on many layers and items of clothing, such as underwear, a scrub suit or pajamas, paper boots, an occlusive/impervious gown, a hat, a hood and often a "space suit" for air exchange. Accordingly, the surgeon becomes very hot due to the many body heat trapping layers of clothing which he or she is wearing. An operating room is typically kept at a temperature which will keep the surgeon comfortable which is from about 20.degree. C. to about 24.degree. C. The surgeon is kept comfortable at the expense of the comfort of the patient. Therefore, a patient is not comfortable in an operating room.
Humans are isothermic or warm-blooded. A healthy human's average body temperature is about 36.5.degree. C. and this body temperature remains within about one degree Celsius, from about 35.5.degree. C. to about 37.5.degree. C., despite wide variations in environmental temperatures. The mechanism by which the human body maintains a constant temperature is called thermal homeostasis. The mechanism is mediated by the hypothalamus of the brain. With a variety of means, the hypothalamus, along with human assistance, keeps the body at a comfortable temperature. Such means are insulation or clothing, ambient temperature control, humidity control and air movement regulation.
A comfortable ambience is one which does not trigger these homeostatic mechanisms, or an environment in which one would feel comfortable wearing clothing suitable to the space, activity and season. The requirements of the surgical operating room differ from most others because clothing suitable to the activity is so different. The patient is relatively naked in the operating room and his or her viscera may be exposed, both of which contribute to the surface exposure of the body to ambient conditions. An operating room is not a comfortable ambience for a patient, due to these and the aforementioned operating room temperature conditions.
An operating room temperature below about 21.degree. C. will typically result in a patient body temperature below about 36.degree. C. This body temperature lowering occurs despite pre-warming of intravenous and irrigation solutions and humidifying anesthetic gases prior to administration to a patient during surgery. Because of the relatively cool operating room temperature, patients undergoing surgery expend a great deal of energy in an effort to maintain body temperature. For the body to fuel its thermoregulatory physiology in an attempt to maintain body temperature, as much as about 40% of a patient's cardiac output may be required. This output is a significant energy expenditure by the body, particularly in an elderly or a debilitated patient.
Accordingly, 20% of patients entering a post-anesthesia room are shivering from hypothermia. A patient is considered hypothermic when his or her body temperature is less than about 35.8.degree. C. The hypothermia results not only from a general or local anesthesia administered for surgery, but also from systemic narcosis due to narcotics administered concomitant with the anaesthetic agent or agents, both of which render a patient poikilothermic or cold-blooded and, thus, reactive to ambient temperatures.
The ability of a patient to maintain homeostasis is further compromised by the fact that a patient wears little if any clothing in an operating room. A patient is fundamentally naked, or at best wears a "johnny shirt", in the operating room. The johnny shirt affords a patient minimal body coverage, is loose-fitting and is made of a cotton or cotton-blend fabric. With all of these factors combined, the johnny shirt has no body heat retention properties.
Patients have been clothed with warm blankets and even encased in metal foil in an attempt to maintain patient body temperature during surgery, but neither of these methods have achieved wide acceptance, except for post-surgery care. In veterinary medicine heated operating tables are used or surgery is carried out on heating pads to maintain the body temperature of the animal. However, neither of these methods are practiced in human medicine, because not enough operating table surface area can be warmed; and there is a larger gradient between operating table temperature and operating room ambient temperature than occurs in veterinary operating rooms.
The problem of maintaining the body temperature of a surgeon and a patient in the operating room has been recognized; however, solutions have been proposed only for maintaining the body temperature comfort of the surgeon. For instance, U.S. Pat. No. 5,027,438 by Schwarze et al., issued on Jul. 2, 1991, for "Operating Room Clothing with Coated Fabric", generally discloses a system of operating room garments for a surgeon. The garment system consists of scrub pants which are worn under a tabard for protection against bacterial transmission. Over both of these garments, a surgical gown is worn which has water repellant, bacteria barrier panels for the sleeves and the chest area (from neck to mid-thigh). The system provides a surgeon with a choice of garment selection, depending upon the surgical procedure involved. Again, the garment of this patent is directed toward the needs of a surgeon, not those of a patient.
The problem of maintaining both surgeon and patient comfort is also recognized by William Beck, M. D., FACS, Thermal Comfort for the Patient During Surgery: Comfort, a Physiological as well as a psychological phenomenon, The Guthrie Journal, Volume 82/No. 4, Fall 1993. Once again though, a solution is provided only for maintaining surgeon comfort. Beck proposes a complete revision of the current gowning and draping system for a surgeon which consists of a light, simple comfortable gown for protection from dry penetration with a plastic over-gown which would cover the front of the torso and arms of the surgeon, thus providing protection from wet penetration. Beck's approach is to make the surgeon comfortable in a room temperature designed more for patient comfort. Yet even with this approach, a patient will still suffer body temperature discomfort, because the patient is minimally clothed and under anesthesia during surgery, both of which contribute to compromising a patient's body temperature.
There is a need to maintain patient body temperature during surgery. Yet, as is evident from the prior art discussed, no solution to this problem has been proposed. Therefore, there is a need for a means by which to maintain patient body temperature in an operating room. The present invention discloses and claims a garment to be worn by a patient in an operating room which assists the patient in maintaining body temperature.